Support all modes of RR deletion by dynamic update

[GoogleCodeExporter]

The DNS dynamic update mechanism allows deletion of 

1) a specific resource-record, 
2) a resource-record set, or 
3) deletion of all records belonging to a name. 

The Route 53 API, however, implements only specific resource-record deletion. 
At present route53d will reject requests for the other deletion types. Instead 
it should query the Route 53 API to find the data it needs to populate a valid 
API request on foot of all dynamic update deletion variants.

Original issue reported on code.google.com by [email protected] on 5 Mar 2012 at 3:38